Step-by-step explanation: We are given that Melia put $20 initially in piggy bank.
Each week amount added in piggy bank = $1.50.
Let us assume total number of weeks be n Melia added amount in piggy bank and get y amount after n weeks.
a) Therefore, total amount after n weeks = Initial amount + 1.50 times n weeks.
y= 20+ 1.50n.
b) On 18th birthday, there would be total 8 years after 10th birthday.
And in 8 years there would be 52 × 8 = 416 weeks.
So, in order to find the total amount after 8 years or 416 weeks, we need to plug n= 416 in the equation we got in a part.
Therefore,
y = 20+ 1.50(416)
y = 20 + 624 = 644.